Parkinson's Disease & Use of Aricept

Parkinson's disease (PD) is a progressive brain and motor disorder with degeneration of neurons (nerve cells) in the substantia nigra in the midbrain. These neurons produce the neurotransmitter (a chemical that carries impulses from one neuron to another) dopamine, and the nigrostriatal fibers carry the dopamine to other parts of the brain. As the substantia nigra degenerates and the fibers become impaired, an imbalance forms between dopamine and acetylcholine (another neurotransmitter), causing tremors and motor impairment. Additionally, according to the Mayo Clinic, over time about 30 to 40 percent of those with PD develop dementia.

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Parkinson's Dementia

According to meta-analysis of many research studies by the Michael J. Fox Foundation for Parkinson's Research, interest in using drugs, such as Aricept, to treat Parkinson's dementia has increased as a number of studies have shown that mild cognitive impairment can occur within one to two years of Parkinson's diagnosis, and that the impairment tends to progress. Once symptoms resemble those of Alzheimer's, the speed of progression of dementia in Parkinson's mirrors that in Alzheimer's disease.

Parkinson's Treatment

Both Parkinson's treatments, such as levodopa, and Alzheimer's treatments, such as Aricept (donezapil), affect neurotransmitters. Typical Parkinson's disease treatment blocks the effect of increased levels of acetylcholine so that the balance between dopamine and acetylcholine normalizes and allows improved motor function, as symptoms of Parkinson's disease become evident when dopamine levels fall below 80 percent of normal.

Aricept

Aricept is a drug developed for the treatment of dementia caused by Alzheimer's disease, the most common cause of dementia. Alzheimer's disease also involves degeneration of brain tissue and disruption in neurotransmitter activity but is associated with decreased levels of acetylcholine rather than increased. Aricept prevents the breakdown of acetylcholine and appears to relieve the symptoms of cognitive impairment (from mild to severe) in some people with Alzheimer's disease. It is also appears to be somewhat effective in treating Parkinson's dementia. The National Institute of Neurological Disorders and Stroke has completed phase IV studies on the effects of Aricept on Parkinson's dementia.

Exelon

According to Parkinson's Action Network, Exelon (rivastigmine), a drug similar to Aricept, has been approved by the FDA for the treatment of Parkinson's dementia. Exelon can be taken orally or through a patch applied to the skin. Journal Watch reported that a review of the Exelon clinical trials showed that significant improvement occurred only in 5 percent of people while Exelon appeared to prevent further deterioration in 10 percent, so the advantages to the drug are modest.

Considerations

While usual treatments for Parkinson's disease tend to have the opposite effect on acetylcholine as Aricept and Exelon, the relationship between Parkinson's treatment and onset of dementia isn't clear.